HP OpenVMS Systems Documentation

HP Pascal for OpenVMS
Language Reference Manual

An identifier is a combination of letters, digits, dollar signs ($), and underscores (_) that conforms to the following restrictions:

• An identifier cannot start with a digit.
• An identifier cannot contain spaces or special symbols.
• The first 31 characters of an identifier must denote a unique name within the block in which the identifier is declared. An identifier longer than 31 characters generates a warning message. The compiler ignores characters beyond the thirty-first character.
• The Pascal standard dictates that an identifier cannot start or end with an underscore, nor can two adjacent underscores be used within an identifier. However, HP Pascal allows both cases of underscore use and generates an informational message if you compile with the standard switch.

On OpenVMS systems, HP Pascal uses uppercase characters for all external user symbols.

You can provide a string argument to the GLOBAL, WEAK_GLOBAL, EXTERNAL, and WEAK_EXTERNAL attributes to override this case usage. HP Pascal passes the string unmodified to the linker.

This manual shows predeclared identifiers in uppercase letters. If you choose, you can express them in mixed case or lowercase in your programs. The following examples show valid and invalid identifiers:

Valid:

For2n8
MAX_WORDS
upto
LOGICAL_NAME_TABLE       {Unique in first}
Logical_Name_Scanner     {  31 characters}

SYS$CREMBX

Invalid:

4Awhile                                   {Starts with a digit}
up&to                                     {Contains an ampersand}
YEAR_END_87_MASTER_FILE_TOTAL_DISCOUNT    {Not unique in first}
Year_End_87_Master_File_Total_Dollars     { 31 characters}

Table 1-5 presents the HP Pascal predeclared identifiers that name data types, symbolic constants, file variables, procedures, and functions. You can redefine a predeclared identifier, but if you do, the original declaration becomes unavailable within the block in which you redeclared the word.

For More Information:

• On attributes (Chapter 10)

Comments document the actions or elements of a program. The text of a comment can contain any ASCII character except a nonprinting control character, such as an ESCAPE character. You can place comments anywhere in a program that white space can appear.

You signify a comment with braces or with a parenthesis and asterisk pair, as follows:

{ This is a comment. }
(* This is a comment, too. *)

HP Pascal allows you to mix the two symbol pairs in one comment, as follows:

{ The delimiters of this comment do not match. *)
(* HP Pascal allows you to mix delimiters in this way. }

HP Pascal does not allow you to nest comments. The following example causes a compile-time error because the comment ends at the first closing delimiter (}).

(* Cannot { nest  comments inside } of comments like this *)

%IF FALSE
%THEN
...code to disable...
%ENDIF

This comment syntax is not recognized by SCA for report generation.

1.4 Page Breaks and Form Feeds in Programs

A page break or form-feed character can appear anywhere in your program except on a line with text surrounding the form feed. For example, the following lines are legal:

[FF]

%TITLE 'Variable Declarations'

end; [FF]
[FF]
[FF] VAR [FF]

However, the following line generates an error:

BEGIN [FF] END

The page break does not affect the meaning of the program, but causes a page to eject at the corresponding line in a listing file.

Every piece of data that is created or manipulated by an HP Pascal program has a data type. The data type determines the range of values, set of valid operations, and maximum storage allocation for each piece of data.

This chapter describes the following topics:

• Section 2.1, Ordinal Types
• Section 2.2, Real Types
• Section 2.3, Pointer Types
• Section 2.4, Structured Types
• Section 2.5, Schema Types
• Section 2.6, String Types
• Section 2.7, Null-Terminated Strings
• Section 2.8, TIMESTAMP Type
• Section 2.9, Static and Nonstatic Types
• Section 2.10, Type Compatibility

For More Information:

• On user-defined types and the TYPE section ( Section 3.5)
• On variable declarations and the VAR section ( Section 3.7)
• On automatic type conversions ( Section 4.4)
• On type conversion functions (Chapter 8)
• Internal representation of data types ( Section A.3)

This section describes the ordinal types that are predefined by HP Pascal and user-defined ordinal types (types that require you to provide identifiers or boundary values to completely define the data type).

The ranges of values for these types are ordinal in nature; the values are ordered so that each has a unique ordinal value indicating its position in a list of all the values of that type. There is a one-to-one correspondence between the values in an ordinal type and the set of positive integers.

2.1.1 Integer Types

HP Pascal makes available the INTEGER, INTEGER64, UNSIGNED, UNSIGNED64, and INTEGER_ADDRESS predeclared types. These data types are described in Section 2.1.1.1, Section 2.1.1.2, and Section 2.1.1.4, respectively.

2.1.1.1 INTEGER and INTEGER64 Types

HP Pascal provides the INTEGER and INTEGER64 (not available on all systems) integer types. Also provided are the INTEGER8, INTEGER16, and INTEGER32 types, which are used as synonyms for subranges of the INTEGER type.

The range of the integer values consists of positive and negative integer values, and of the value 0. The range boundaries depend on the architecture of the machine you are using.

Table 2-1 lists the storage sizes and ranges of values for these signed ordinal types.

The largest possible value of the INTEGER64 type is represented by the predefined constant MAXINT64. The smallest possible value of the INTEGER64 type is represented by the value of the expression -MAXINT64. While the value of -MAXINT64-1 can also be represented, correct results may not be produced in certain expressions.

The largest possible value of the INTEGER type is represented by the predefined constant MAXINT. The smallest possible value of the INTEGER type is represented by the value of the expression -MAXINT. While the value -MAXINT-1 can also be represented, it may not produce correct results in certain expressions.

Table 2-2 lists the sizes and the corresponding values of MAXINT and MAXINT64.

Table 2-3 lists the range of values for unsigned numbers.

Table 2-4 lists the sizes and the corresponding values of MAXUNSIGNED and MAXUNSIGNED64.